Around 15,000 years ago - there weren't any cities in North America.
Instead the continent was covered with grassland and forest land.
And according to new research - there was a lot more poop from large animals all around.
And that poop nourished life on Earth.
New research from researchers at the University of Vermont shows that feces from animals are essential in moving nutrients up the food chain.
The research was published in the Proceedings of the National Academy of Sciences - and it points to a wide array of animals involved in the nutrient cycle - including whales - seabirds - animals that graze on land - and large predators.
The study is more than just a fun reason to talk scatological, though - it's also a dire warning about how human activities are leading to an impending breakdown of our planet's food web and nutrient cycles.
If we go back 15,000 years - the North American continent was home to mammoths and mastodons - elk and moose - and large carnivores like the saber tooth cat and the dire wolf.
All of these animals acted as a "distribution pump" with their feces - transporting nutrients from "hot spots" to other places.
And the distribution of nutrients works two ways - both up through the food chain biologically - and across the continent geographically.
Take my friend Stuart Pimm's example of a discovering how bear poop is essential to forest health in the Pacific Northwest.
Forests in the Pacific Northwest were lacking iodide in their soil - which trees in that area need to survive.
It was already interesting that the trees required iodide - which comes from the ocean - when the forests were very clearly inland.
But even more interesting was the fact that the forests suddenly started growing back - and that the soil was getting more and more iodide.
So what happened?
